DFT study of cobalt porphyrin complex for living radical polymerization of olefins

We design versatile cobalt porphyrin complexes for living radical polymerization (LRP) of olefins and perform density functional theory (DFT) calculations to investigate the efficiency of cobalt porphyrin complexes. Our calculation results demonstrate that (TMP-OH)Co-R is efficient due to less steric hindrance. By comparing the bond dissociation energies (BDEs) and reaction pathways, our calculation results show that the efficiency of cobalt porphyrin complexes is in the following sequence: (TPFP)Co-R > (TMP-OH)Co-R > (TMP)Co-R. We find that electronic effect and steric hindrance are important for bond dissociation energies of cobalt porphyrin complexes. Among the chosen monomers, Co-C-R BDEs of VAc and AN are the highest, and tBA's is the lowest, which determines their performance in LRP. The polydispersity index (PDI) of these polymerized olefins we obtained is consistent with our calculated BDE. We conclude that the activation barrier of the radical pair correlates with the catalytic efficiency. Low activation barrier corresponds to efficient catalytic reaction. Our results show that the modified species (TMP-OH)Co-II and (TPFP)Coll are better LRP catalysts for olefins than (TMP)Co-II. (C) 2012 Elsevier B.V. All rights reserved.